At ShapeStart I've found it very useful to have an up to date capitalization table (cap table). If you are not familiar, it is a document, or more often a spreadsheet, that lists the ownership of a corporation. It can also list the price of that ownership, either how much they paid, or how much they would be paid in the event of an exit.
Cap tables are useful in setting up an option pool for your employees, figuring out how much money to raise or how much you can raise. They can also show you how ownership and or value will change with a sale of shares, etc. There are a ton of ways to organize this information and probably a bunch of sample spreadsheets to download for free. There may not be too many on google docs and since I use mainly google docs I figured I would share a public version of my cap table.
It should look something like this:
;)